Radiation imaging cassette

ABSTRACT

A radiation imaging cassette. The cassette includes a housing, a latch member, and guide edges. The housing is adapted to house a stimulable phosphor sheet. The housing includes a light-protected region and an opening for extraction and/or insertion of the stimulable phosphor sheet. The latch member releasably engages the stimulable phosphor sheet to secure at least a portion of the stimulable phosphor sheet within the light-protected region. The edge guides are disposed within the housing and operate to guide movement of the stimulable phosphor sheet through the opening.

FIELD OF THE INVENTION

The invention generally relates to computed radiography, and inparticular to an apparatus for scanning a stimulable phosphor mediumhaving an exposed radiographic image formed thereon.

BACKGROUND OF THE INVENTION

The field of computed radiography (CR) is well known. In computedradiography, x-rays are directed through a subject and onto a stimulablephosphor storage medium that stores a resulting image. The stimulablephosphor medium is subsequently provided to a scanning/reader apparatus,where the stimulable phosphor medium is stimulated to emit a radiationpattern that is indicative of the image formed by the x-rays.Advantageously, the stimulable phosphor medium can be erased andre-used.

In one arrangement of the stimulable phosphor storage medium, thestimulable phosphor medium is a flexible sheet suitable for transportthrough a scanning apparatus. For example, U.S. Pat. No. 6,770,900(Minagawa) entitled “Mechanical [Apparatus] for Discharging Sheet-LikeMember Container” describes an apparatus that guides a flexible sheetfrom a cassette and past a scan head and erasure apparatus, returningthe erased flexible sheet into the cassette. U.S. Pat. No. 5,265,865entitled “Stimulable Phosphor Sheet Feeding and Storing Mechanism andStimulable Phosphor Sheet Cassette” (Agano) describes a scanningapparatus for automating the reading function and a cassette mechanismthat holds the stimulable phosphor sheet during imaging, shipment, orstorage.

An alternative arrangement to the flexible sheet is a computedradiography medium formed from a rigid sheet/plate. A rigid stimulablephosphor storage medium has advantages over flexible sheets, includingdurability and ease of handling. As a further benefit, a rigid substrateworks well for needle phosphors, advantaged over other phosphor shapesin digital radiography for its imaging characteristics. Rigid stimulablephosphor storage media is described in U.S. Pat. No. 6,784,448(Neriishi) entitled “Method for Reading Radiation Image from StimulablePhosphor Sheet” which describes a scanning apparatus and methodemploying a rigid sheet. Commonly assigned U.S. Pat. No. 6,437,359(Hall) entitled “CR Reader with Vertical Scanning” describes using avertical travel path for directing a stimulable phosphor medium pastscanning and erasure components. Commonly assigned U.S. Pat. No.6,683,315 (Wendlandt) entitled “Storage Phosphor Cassette” and U.S. Pat.No. 5,276,333 (Robertson) entitled “X-Ray Cassette Having RemovablePhotographic Element” describes embodiments of cassette apparatus for arigid stimulable phosphor sheet.

An advantage of the rigid stimulable phosphor medium relates to the“footprint” or area required by the reader apparatus for scanning therigid medium in automated fashion. One example proposed for minimizingfootprint is given in U.S. Pat. No. 6,949,759 (Yonekawa) entitled“Radiographic Image Reading Apparatus”, which describes a pivoting feedand registration mechanism with complex mechanisms for internal handlingof the rigid stimulable phosphor medium.

Apparatus have been investigated for providing automated scanning andprocessing of rigid stimulable phosphor medium, however, cost andmechanical complexity can be significant drawbacks. Accurateregistration of the scanning apparatus to the imaged stimulable phosphormedium needs to be maintained. Even where a straightforward transportpath is maintained for handling the stimulable phosphor medium, it canbe difficult to maintain proper registration of the scanning apparatusto the stimulable medium without adding cost and complexity.

Accordingly, it is desired to provide a cassette for use with anscanning apparatus which provides accurate scanning registration,reduces the footprint, and is relatively low cost.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided aradiation imaging cassette. The cassette includes a housing, a latchmember, and guide edges. The housing is adapted to house a stimulablephosphor sheet. The housing includes a light-protected region and anopening for extraction and/or insertion of the stimulable phosphorsheet. The latch member releasably engages the stimulable phosphor sheetto secure at least a portion of the stimulable phosphor sheet within thelight-protected region. The edge guides are disposed within the housingand operate to guide movement of the stimulable phosphor sheet throughthe opening.

These and other objects, features, and advantages of the presentinvention will become apparent to those skilled in the art upon areading of the following detailed description when taken in conjunctionwith the drawings wherein there is shown and described an illustrativeembodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter of the present invention, itis believed that the invention will be better understood from thefollowing description when taken in conjunction with the accompanyingdrawings, wherein:

FIG. 1 shows a side view of a radiation image data reading apparatusaccording to the present invention.

FIG. 2 is a side view of the radiation image data reading apparatusshowing internal subsystems and components.

FIG. 3 is a perspective view of the radiation image data readingapparatus with cover removed.

FIG. 4 is a front view of the radiation image data reading apparatuscomponents.

FIG. 5 is a close up view showing key components of the transportsection and its associated scanning section.

FIG. 6 is a perspective view showing cassette handling components.

FIG. 7 is a perspective view showing the substantially verticaltransport path for the stimulable phosphor sheet.

FIG. 8 is a close-up perspective view of transport section components.

FIGS. 9A through 9F show the sequence of handling for the stimulablephosphor sheet.

FIG. 10 shows edge registration along the transport path.

FIG. 11 is a perspective view showing the cassette.

FIG. 12A is a cross sectional view of a portion of the cassette showingedge guidance features.

FIG. 12B is a cross sectional view, taken orthogonally with respect toFIG. 12A, showing the leading edge of the phosphor sheet in thecassette.

FIG. 13 is a close-up perspective view showing the cassette latchingmechanism.

FIG. 14A is a close-up perspective view showing the cassette sheetreturn mechanism.

FIG. 14B is a close-up perspective view showing the cassette sheetreturn mechanism at one stage of actuation.

FIG. 14C is a close-up perspective view showing sheet return member 38and support components when actuated.

FIG. 14D is a close-up side view showing sheet return member 38 andsupport components when actuated.

FIG. 15 is a schematic view showing key aspects of gimbaled mounting forscanning and transport components.

FIG. 16 is a perspective view showing components used for gimbaledmounting.

FIG. 17 is a front view showing components used for gimbaled mounting ofthe scanning section.

FIG. 18 is a close-up perspective view of an urging mechanism forreversing sheet direction according to one embodiment.

FIG. 19 is a close-up perspective view of a mechanism for sheet releasefrom the cassette in one embodiment.

FIG. 20 is a side view of the cassette sheet release mechanism.

DETAILED DESCRIPTION OF THE INVENTION

The present description is directed in particular to elements formingpart of, or cooperating more directly with, apparatus in accordance withthe invention. It is to be understood that elements not specificallyshown or described may take various forms well known to those skilled inthe art.

Reference is made to commonly assigned application U.S. Ser. No. (KodakDocket No. 89609), entitled “APPARATUS FOR SCANNING STIMULABLE PHOSPHORMEDIUM”, and filed on common date in the names of Urbon et al., andwhich is assigned to the assignee of this application.

Reference is made to commonly assigned application U.S. Ser. No. (KodakDocket No. 92908), entitled “A SHEET SCANNING APPARATUS”, and filed oncommon date in the names of Urbon et al., and which is assigned to theassignee of this application.

It is noted that a “rigid” or “semi-rigid” phosphor sheet relate tosubstrate media, and may be of particular use with needle phosphors.Some CR systems use a flexible phosphor sheet. The rigidity or stiffnessof a sheet is conventionally characterized as the product of its elasticmodulus E and the cubed value of the sheet thickness t, that is: Et³

As a guideline, a sheet that would be considered at least semi-rigid inthis application would have a modulus of elasticity E of at least500,000 psi and thickness t ranging from about t=0.02 to about t=0.5inches.

Referring to FIG. 1, there is shown, in side view, a radiation datareading apparatus 10 according to the present invention. Radiation datareading apparatus 10 reads a radiographic image that has been obtainedusing an x-ray system (not shown) and has been stored on a stimulablephosphor medium that is housed within a cassette 20. Cassette 20 isdesigned to seat in a receiving/loading section 12 that includes thecomponents to extract the stimulable phosphor medium from cassette 20and restore it into position once a scanning and an erasure process arecomplete. Scanning and erasure components are housed in ahousing/chassis 14.

The side view of FIG. 2 shows internal subsystems of radiation datareading apparatus 10, including a substantially vertical transport paththat a rigid or semi-rigid stimulable phosphor sheet 18 follows fromcassette loading section 12 through portions of chassis 14.

The internal subsystems include a scanning section 16, a transportsection 30, and an erase section 22. Scanning section 16 includesoptics, stimulating radiation, and detector components for obtaining theimage stored on stimulable phosphor sheet 18. Transport section 30,which can be actuated by one or more drive motor(s) 44, guidesstimulable phosphor sheet 18 past scanning section 16 and into erasesection 22. Erase section 22 includes one or more erasure radiationsources 24, typically arranged as a bank of lights, as shown in FIG. 2.Transport section 30 is mechanically coupled to scanning section 16 andcooperates with scanning section 16 to provide precision registration tomove stimulable phosphor sheet 18.

A power supply 26 and control electronics section 28 provide the powerand control signals needed to obtain the image and handle the scanning,erasure, and return of stimulable phosphor sheet 18 into cassette 20.Arrows in FIG. 2 indicate the flow of cooling air provided by a fan 98.

FIG. 3 shows a perspective view, with portions of chassis 14 removed toillustrate underlying parts of radiation data reading apparatus 10,including scanning section 16. Scanning section 16 includes a scanhousing 32 that encloses an optical scanning apparatus 34, indicated indotted outline in FIG. 3, and supports components of transport section30, as described subsequently.

Optical scanning apparatus 34 are known to those skilled in the art, andcan be, for example, a flying-spot scanner that directs a scanned laserlight onto stimulable phosphor sheet 18 as an excitation light, thenreads the excited light that results to obtain the previously storedimage therefrom. Optionally, optical scanning apparatus 34 can be aswath scanning apparatus that uses an excitation source and aphotosensor array for obtaining the stored image, one horizontal swathat a time. The apparatus of the present invention is well-suited tooperation with a number of optical scanning components that directexcitation energy of a first wavelength onto the phosphor sheet 18 andobtain phosphorescent light excited thereby, as is well known to thoseskilled, in the digital radiographic imaging arts.

FIG. 3 also shows a transport roller 36 that is part of transportsection 30 and is used, in conjunction with other components asdescribed subsequently, to move stimulable phosphor sheet 18 throughscanning section 16 and, following scanning, into erase section 22.

In an embodiment shown in FIG. 4, erase section 22 includes a bank oferasure radiation sources, such as would be provided by standardfluorescent lamps, for example a DULUX™ type bulb from Osram Sylvania,Danvers, Mass.

The view of FIG. 5 and rear perspective view of FIG. 6 show transportsection 30. In this embodiment, three pairs of opposing rollers 36 areused for guiding stimulable phosphor sheet 18 through radiation datareading apparatus 10, each pair of rollers 36 forming a nip 40. Withthis arrangement, stimulable phosphor sheet 18 is stably secured betweenat least two nips 40 while it is being scanned. Rollers 36 are attachedto scan housing 32, thereby providing registration along the opticalaxis (conventionally described as the z axis direction).

FIGS. 5 and 6 also show the position of a sheet return member 38 in oneembodiment. Sheet return member 38 is actuated upon return of stimulablephosphor sheet 18 into cassette 20, in the cassette reloading sequencedescribed subsequently.

Sheet Transport Sequence

The perspective view of FIGS. 7 and 8 show scanning section 16 withrollers 36 from transport section 30 mounted onto scan housing 32. Thisarrangement provides registration along the optical axis, shown as the zaxis using the coordinate axes assignment of FIG. 8. The y axis isvertical, the x axis horizontal using this conventional axis assignment.The sequence given in FIGS. 9A through 9F shows how these componentscooperate to transport stimulable phosphor sheet 18 along the vertical yaxis through scanning section 16 and erase section 22. Stimulablephosphor sheet 18 is shown in dotted outline where it is hidden fromview.

FIG. 9A shows stimulable phosphor sheet 18 housed in cassette 20 ascassette 20 is received in cassette loading section 12. Components ofcassette loading section 12, described subsequently, release stimulablephosphor sheet 18 from cassette 20 when cassette 20 is received incassette loading section 12. Nip 40 of the first set of rollers 36receives the leading edge of the released stimulable phosphor sheet 18as it is removed from cassette 20. In one embodiment, controlelectronics section 28 (FIG. 2) detects this leading edge and actuatesone or more drive motors 44 to turn rollers 36 for transportingstimulable phosphor sheet 18. In another embodiment, components ofcassette loading section 12, as described subsequently, actuate a drivemotor when cassette 20 is received in position in cassette loadingsection 12.

Referring next to FIG. 9B, scanning begins when stimulable phosphorsheet 18 has reached a scan position, for example, when sheet 18 reachesthe second nip 40. In this arrangement, stimulable phosphor sheet 18 ispositioned between at least two nips 40, and scan housing 32 isregistered to stimulable phosphor sheet 18. As such, a portion of sheet18 (adjacent the leading edge of the stimulable phosphor sheet) is notused for image storage but rather serves to facilitate handling of thesheet. In one embodiment, for example, the non-imaged lead edge portionof stimulable phosphor sheet 18 is nominally about 0.5 inches,preferably at least more than about 0.25 inches in length.

FIG. 9C shows stimulable phosphor sheet 18 at a position near the end ofscanning. The sheet can be accurately scanned when held between two nips40 as shown. As shown in FIG. 9D, stimulable phosphor sheet 18 reachesan end point 42 of travel, indicated along a dotted line in this figure.At this stage of processing, stimulable phosphor sheet 18 is withinerase section 22 as was shown in FIGS. 2 through 4, and erasure of thesheet can be conducted. After erase exposure is completed, an urgingmechanism 46 is actuated, wherein the direction of stimulable phosphorsheet 18 is reversed and sheet 18 is moved into nip 40 of the lower setof rollers 36. Motor 44, or its supporting gear mechanism (not shown),reverses the direction of rollers 36. Urging mechanism 46 can be acam-actuated arm in one embodiment or alternately a solenoid or otheractuator known to those skilled in the art.

Urging mechanism 46 can be configured to align sheet 18 toward a planesubstantially parallel to reference edge 72. As such, when sheet 18 isinserted into cassette 20 (during reinsertion), sheet 18 is urged towardreference edge 72. For example, as shown in FIG. 18, lifting arm 108 canbe an urging-surface which moves along the x-axis edge of sheet 18toward the plane substantially parallel to reference edge 72 therebycausing sheet 18 to slightly pivot and translate in the x-directiontoward the plane substantially parallel to reference edge 72.

FIG. 9E shows stimulable phosphor sheet 18 moving through rollers 36 andinto cassette 20. Edge guidance can be provided for guiding side edgesof stimulable phosphor sheet 18 along its return path to promote sheetreinsertion into cassette 20 without binding or obstruction. FIG. 9Fshows completion of the reinsertion sequence. Sheet return member 38actuates to urge stimulable phosphor sheet 18 into cassette 20. Once thesheet is returned to the cassette, a latch mechanism can be engaged tosecure the sheet within the cassette, as is described subsequently.

As was described with reference to FIG. 2, control electronics section28 can provide the control logic and drive signals that coordinatemovement of stimulable phosphor sheet 18 along its transport path. Aminimum number of sensors are needed to detect conditions such as end oftravel, presence within at least two nips 40, and other events, as wouldbe familiar to one skilled in the motion control arts.

Rollers 36 can be conventional paired rollers, for example, with rubberand foam rollers paired to form nip 40 which are preferably firm but notoverly rigid. The rollers are employed to hold stimulable phosphor sheet18 firmly, without causing it to fold, bend, or become warped.

FIGS. 14A through 14D show an embodiment of sheet return member 38. FIG.14A shows sheet return member 38 in a resting or unused position. Uponsensing that stimulable phosphor sheet 18 is being reinserted intocassette 20, sheet return member 38 is actuated. The perspective viewsof FIGS. 14B and 14C and side view of FIG. 14D show sheet return member38 in a actuated position. Members 96, shown as spread fingers 96, onsheet return member 38 are arranged to stabilize edge movement as sheetreturn member 38 urges the leading edge of stimulable phosphor sheet 18upward toward cassette 20. A motor 94 and support hardware, such aspivoted lifting arms 76 having pivot points 74 (as shown in FIGS.14A-14D), cooperate to move sheet return member 38 upward. A gap 78 inupper roller 36 allows unobstructed travel of sheet return member 38past transport components.

In moving stimulable phosphor sheet 18 into an opening 50 of cassette20, sheet return member 38 re-engages the restraint/latch mechanism thatsecures stimulable phosphor sheet 18 within cassette 20, as described inmore detail subsequently.

It is noted that sheet return member 38 can force cassette 20 slightlybut noticeably out of position in cassette loading section 12, so thatan operator can visually ascertain that scanning and reinsertion arecompleted.

By way of reference, FIG. 14B shows, using arrow F, the direction offorce applied to cassette 20 to obtain edge registration, as describedwith regard to FIG. 10.

FIG. 18 more particularly illustrates urging mechanism 46 that reversesthe movement direction of stimulable phosphor sheet 18 at the end oftravel (end point 42 of FIG. 9D). For the arrangement shown in thefigure, motor 104 actuates a lifting mechanism 106 that pushes a liftingarm 108 upward. It is noted that a minimal/small amount of upwardmovement is needed, since reversal of roller 36 direction in transportsection 30, as described earlier, moves stimulable phosphor sheet 18 inthe direction for reloading into cassette 20. A number of differentlifting 30 mechanisms 106 can be employed for this function, as will bewell known to those skilled in the motion control arts.

Sheet Registration

As illustrated in FIGS. 9A through 9F, proper registration of stimulablephosphor sheet 18 and guidance along its transport path promotesaccuracy of image scanning and provides the precision for automatedreinsertion into cassette 20. The perspective view of FIG. 10 shows thetransport path of stimulable phosphor sheet 18 with coordinate axes forreference. Rollers 36 cooperate to stabilize the position of stimulablephosphor sheet 18 with respect to the xy plane and set the proper z axisdistance to scanning optics. Registration of the cassette and plate isaccomplished using a single registration edge, as will be describedbelow with reference to edge 72.

Cassette

FIGS. 11, 12A, 12B, and 13 show particular features of cassette 20relative to the scanning sequence described with reference to FIGS. 9Athrough 9F. Opening 50 exposes a lead edge 62 of stimulable phosphorsheet 18, as is best shown in FIG. 12B. Lead edge 62 provides a portionof stimulable phosphor sheet 18 that extends out from opening 50, beyonda light-protected region, and allows manipulation and guidance ofstimulable phosphor sheet 18 through transport section 30, as describedearlier. Lead edge 62 is a non-imaged area. That is, lead edge 62 is notconsidered as part of the “imageable” area of stimulable phosphor sheet18; imageable portions are protected from ambient light by enclosurewithin the light-protected body of cassette 20.

To provide enclosure for stimulable phosphor sheet 18 that issubstantially light-tight, cassette 20 has top and bottom covers 52.Left and right side extrusions 54 support covers 52 and have edge guidefeatures 60, shown in transverse cross section in FIG. 12A, that canextend along the length of stimulable phosphor sheet 18. Stimulablephosphor sheet 18 itself includes a phosphor coating 58 on a plate 56.It is noted that a tolerance is accommodated between the edge ofstimulable phosphor sheet 18 and edge guide features 60 on sideextrusion 54.

FIG. 13 shows an edge of cassette 20 with side extrusion 54 removed, toallow visibility of a restraining latch mechanism 64 used for securingin place or releasing stimulable phosphor sheet 18 within cassette 20.Mechanism 64 is one suitable type of restraint member and can bespring-held or otherwise forced inward to engage a notch/detent 66 alongan edge of stimulable phosphor sheet 18. Other suitable mechanisms willbe known to those skilled in the art.

FIGS. 19 and 20 show a latch release 70 on cassette loading section 12,with a portion of the obstructing hardware removed for illustrativepurposes. In the arrangement shown, a spring 100 exerts a spring forcethat cooperates with a pivot point 102 so that latch release 70 pressesinward, toward cassette 20. Latch release 70, acting as a releasemember, pivots restraining latch 64 on cassette 20 when the operatorinserts cassette 20 into a cassette feed slot 68 (slot 68 is shown inFIG. 14A, and is a component of cassette loading section 12). Inaddition, the force exerted against cassette 20 urges it against an edge72 (of cassette loading section 12, as shown in FIGS. 6 and 14A) whichaligns cassette 20. Thus, inserting cassette 20 into slot 68 (ofcassette loading section 12) provides the release of stimulable phosphorsheet 18 from cassette 20 for scanning and alignment of cassette 20 intoedge registration (in the x direction of the yz plane) in the transportpath.

It is noted that cassette 20 can be registered in the z direction (ofthe xy plane) by the addition of a mechanical force, for example, aspring or plunger. This may be desirable if the opening of cassette feedslot 68 is enlarged for manufacturability purposes or for ease ofcassette insertion by an operator.

In one arrangement, a sensor (not shown) detects travel of latch release70 to initiate operation of transport section 30 motors when cassette 20is installed into cassette feed slot 68. A limit switch or other sensorcan be used to detect latch release 70 movement, using techniques andpractices known to those skilled in the motion control arts.

In the embodiments shown herein, latch release 70 actuates automaticallyto release stimulable phosphor sheet 18. Alternatives include coupling asolenoid or other actuator to latch release 70 to release stimulablephosphor sheet 18 under command from control electronics section 28(FIG. 2).

Gimbaled Scan Mounting

Radiation data reading apparatus 10 has a gimbaled scanning apparatusthat enables scan housing 32 (FIG. 8) to register to stimulable phosphorsheet 18 without overconstraint. With this mounting arrangement, scanhousing 32 allows a number of degrees of freedom for registration,including allowing some movement along z and x axes and rotation aboutthe x axis (θ_(x)) and y axis (θ_(y)). Movement in y and rotation aboutthe z axis (θ_(z)) are constrained in this arrangement.

FIG. 15 shows schematically scan housing 32 (represented as arectangular box, without showing rollers 36 of transport section 30attached) supported from the frame of chassis 14 to provide gimbaledaction.

FIGS. 16 and 17 show, in front and perspective views respectively,hardware components used to effect this gimbaled arrangement. Along anaxis A, parallel to the x axis as shown, scan housing 32 is supported attwo suspension points, at the right 82 r and at the left 82 l. A thirdsuspension point 80 is suspended by a flexible coupling 88, such as aspring, from a fixed point 86 on the frame of chassis 14. Flexiblecoupling 88 allows a measure of rotation about the x axis (θ_(x)) andback and forth movement generally in the z direction, as indicated by adotted line C. Hinges 90r and 901 support suspension points 82 r and 82l respectively, allowing a measure of rotation as indicated by a dottedline D. Best shown in FIG. 16, pins 92 r and 92 l that extend from scanhousing 32 are supported within hinges 90 r and 90 l, each providingessentially a single point of contact. A slight amount of movement inthe direction of the x axis is permitted by this arrangement. Flexiblecoupling 88 is adjustable in one embodiment, enabling fine-tuning of theoverall stiffness and angular response range of the gimbaled mount.

Hinges 90 r and 90 l suspend scan housing 32 from stationary hingepoints 84 r and 84 l, respectively. This allows some rotational movementas indicated by a dotted line E, effectively providing movement in thedirection of the optical axis z, with the cooperation of flexiblecoupling 88. It can be observed that this arrangement constrainsmovement in the direction of the vertical axis y and constrainsrotational movement about the optical axis z (θz), while allowing somemeasure of movement along z and x axes and rotation about the x axis(θ_(x)) and y axis (θ_(y)).

As is shown in FIGS. 16 and 17, transport section 30, with rollers 36,is attached to scan housing 32, with each roller 36 axially coupled toallow its rotational movement. Thus, when stimulable phosphor sheet 18is held between at least two nips 40, scan housing 32 registers to thesurface of stimulable phosphor sheet 18 in a gimbaled manner.

Referring back to FIG. 15, it can be appreciated that the gimbaledsupport of scan housing 32 can be effected in a number of ways, butstill operate according to the basic principles described earlier. Forexample, flexible coupling 88 need not be a spring, but can begeneralized to be a coupling that allows some measure of movement inrotation about the x axis (θ_(x)) and movement along the optical axis z.Flexible coupling 88 could suspend scan housing 32 from above as shownin FIG. 15 or could flexibly support scan housing 32 by protruding frombelow.

With respect to the horizontal axis x, support point 80 is betweensupport points 82 l and 82 r. The couplings used for support points 82 land 82 r extend from the supporting frame to the scan housing andprovide axial alignment of scan housing 32 relative to the horizontalaxis x. Couplings to support points 82 l and 82 r must allow somemeasure of rotation θ_(x) about the horizontal axis x, at least about 2degrees, but preferably 5 degrees or more rotation.

Support points 82 l and 82 r can be supported by suspension from theframe, as depicted in FIG. 15 and shown in the hinged arrangement ofembodiments in FIGS. 16 and 17. Alternate arrangements for supportingscan housing 32 at these points can include support from below, such asball-and-socket support or hinged support, including using a rotatableplatform, for example. Whatever gimbaled movement is provided, it isimportant to support scan housing 32 to constrain movement in the ydirection, for example by using gravity to support points 82 l and 82 r,and to constrain rotation about the optical z axis, or θ_(z). Rollers 36of transport section 30 are mechanically coupled to scan housing 32,with this 3-point coupling arrangement allowing the gimbaled action thatconforms the position of scan housing 32 relative to the surface ofstimulable phosphor sheet 18.

Radiation data reading apparatus 10 as described herein is advantagedfor providing controlled guidance of stimulable phosphor sheet 18 alonga substantially vertical transport path, minimizing the equipmentfootprint where floor space is at a premium. Automated extraction,scanning, erasure, and return of stimulable phosphor sheet 18 withcassette 20 allows enhanced efficiency of operation, since the operatorneed only insert cassette 20 into cassette loading section 12 and removecassette 20 when the scanning and erasure operations have beencompleted. Compared with conventional scanning solutions, as describedearlier in the background section, the apparatus of the presentinvention offers a low-cost solution, using gravity feed and offeringrepeatable operation.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the scope of theinvention as described above, and as noted in the appended claims, by aperson of ordinary skill in the art without departing from the scope ofthe invention. For example, various types of rollers could be employed.Various types of sensing devices could be used to detect the presence ofthe phosphor sheet in roller nips. Various types of scanning excitationsources and photoelectric detectors, familiar to those skilled in thediagnostic imaging arts, could be used. The apparatus of the presentinvention is particularly suitable where the stimulable phosphor sheetis at least semi-rigid, as defined earlier.

Thus, what is provided is an apparatus and method for scanning astimulable phosphor medium having an exposed radiographic image thereon.

The invention has been described in detail with particular reference toa presently preferred embodiment, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention. The presently disclosed embodiments are thereforeconsidered in all respects to be illustrative and not restrictive. Thescope of the invention is indicated by the appended claims, and allchanges that come within the meaning and range of equivalents thereofare intended to be embraced therein.

PARTS LIST

-   10. Radiation data reading apparatus-   12. Cassette loading/receiving section-   14. Chassis-   16. Scanning section-   18. Phosphor sheet-   20. Cassette-   22. Erase section-   24. Erasure radiation source-   26. Power supply-   28. Control electronics section-   30. Transport section-   32. Scan housing-   34. Optical scanning apparatus-   36. Transport roller-   38. Sheet return member-   40. Nip-   42. End point-   44. Motor-   46. Urging mechanism-   50. Opening-   52. Cover-   54. Side extrusion-   56. Plate-   58. Phosphor coating-   60. Edge guide features-   62. Lead edge-   64. Latch-   66. Detent-   68. Slot-   70. Latch release-   72. Edge-   74. Pivot point-   76. Lifting arm-   78. Gap-   80, 82 r, 82. Support point-   84 r, 84 l. Hinge points-   86. Fixed point-   88. Flexible coupling-   90 r, 90 l. Hinge-   92 r, 92 l. Pin-   94. Motor-   96. Finger-   98. Fan-   100. Spring-   102. Pivot-   104. Motor-   106. Lifting mechanism-   108. Lifting arm-   A, B. Axis-   C, D, E. Dotted line-   F. Arrow

1. A cassette, comprising: a housing adapted to house a stimulablephosphor sheet, the housing including a light-protected region and anopening for extraction and/or insertion of the stimulable phosphorsheet; a latch member for releasably engaging the stimulable phosphorsheet to secure at least a portion of the stimulable phosphor sheetwithin the light-protected region; and edge guides disposed within thehousing to guide movement of the stimulable phosphor sheet through theopening.
 2. The cassette of claim 1 wherein a lead portion of thestimulable phosphor sheet extends outside of the light-protected regionof the housing.
 3. The cassette of claim 2 wherein the lead portion isat least 0.25 inches in length.
 4. The cassette of claim 1 wherein thehousing further including a non-light-protected region adjacent theopening, and a lead portion of the stimulable phosphor sheet is disposedin the non-light-protected region when the at least a portion of thestimulable phosphor sheet is secured within the light-protected regionby the latch member.
 5. The cassette of claim 1 wherein the latch memberinclude a spring.
 6. The cassette of claim 5 wherein the spring biasesthe latch member into engagement with the stimulable phosphor sheet. 7.The cassette of claim 1 wherein the latch member is disposed on a sideof the cassette, and is configured to releasably engage a detentdisposed in the sheet.
 8. The cassette of claim 1 wherein the edgeguides are disposed within the housing along two opposing edges.
 9. Thecassette of claim 1 wherein the edge guides constrain movement of thesheet in a direction substantially normal to an extraction/insertiondirection.
 10. A cassette handling section of a radiation readingapparatus, comprising: a loading section adapted to receive a cassettehousing a sheet; a latch release adapted to actuate a pivotable latchdisposed on a side of the cassette to release the sheet housed withinthe cassette; and a guidance apparatus accepting the released sheet fromthe cassette and guiding the sheet out of the cassette.
 11. The cassettehandling section of claim 10 wherein the guidance apparatus guides thesheet in a substantially vertical direction and comprises at least threesets of opposed rollers.
 12. The cassette handling section of claim 10wherein the loading section is configured to urge the cassette against areference edge to register the sheet.
 13. The cassette handling sectionof claim 10 wherein the latch release includes a spring cooperating witha pivot point.
 14. The cassette handling section of claim 10 wherein thelatch release is configured to urge the cassette toward a referenceedge.